The present invention relates to a similar-image retrieving apparatus and similar-image retrieving method for retrieving similar images in image database equipment or the like, and also relates to program storage media therefor.
In recent years, with a remarkable development in the information processing field, and particularly with improvement in performance of personal computers or the like, image database equipment and electronic filing equipment have been becoming widespread not only for business use and special use but also for general users. In these equipment, an image is captured by an input device as image data, and the captured image data is stored and managed together with additional information such as a key word, and afterwards, as required, retrieved and printed by an output device. The additional information for image data includes attribute information such as preparation date, correction date, file name and file format, and key information such as key word, shape feature, hue and speech. Then, in the image database equipment or electronic filing equipment, a desired image is retrieved by specifying the attribute information and the key information, while comparison operation of image data itself is performed for retrieving an image closely similar to a particular key image.
However, in the image database equipment or the electronic filing equipment as described above, since comparison operation of the image data itself is performed for the retrieval of a similar image, a large amount of memory resources are involved in the storage of image data, while enormous memory and processing time are required for the comparison. Thus, those equipment could not be practical systems.
This being the case, there has been proposed a similar-image retrieving apparatus in which a similar image is retrieved using edge information of images ("Retrieval of image contents, Kato and Kurita", Journal of Information Processing Society, Vol. 33, No. 5). However, shape comparison by edge images in this similar-image retrieving apparatus has a disadvantage that the degree of extraction for external shape is so low that similar images having a rotated or translated external shape or having a scaled-up or scaled-down external shape could not be retrieved. Also, because the feature quantity of an extracted shape is represented by image data, large amounts of memories are required for storage of data, while large amounts of operations are involved in the retrieval of an image, so that long time would be required for retrieval, as a further problem.